Although shivering is a universal sign of feeling chilly, it is actually an evolved response to keep us alive.

If the temperature of our internal organs falls much below 37 degrees Celsius (99 degrees Fahrenheit), we could die of hypothermia.

When the brain detects that we are cold enough that this might happen, it stimulates muscles to jiggle slightly. In moderately low temperatures this creates enough heat to keep our organs from slowing down. It also makes us tremble. Shivering consumes energy and only works when it isn’t extremely cold.

Nevertheless, it’s more likely to keep us alive than a mug of hot chocolate!

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